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High-resolution Micro-Computed-Tomography Zone of Injury Characterization of Simulated Lacerations to Peripheral Nerve
Safa Bauback, MD
1; Brandon S. Smetana, MD
2; Adam B Strohl, MD
3; Sunishka M. Wimalawansa, MD, MBA
4; Eitan Melamed, M.D.
5; Amy M Moore, MD
6; Fraser J. Leversedge, MD
7; Youssra Marjoua, MD
8; Rasa Zhukauskas, MD
91The Buncke Clinic, The Buncke Clinic, San Francisco, CA; 2Indiana Hand to Shoulder Center, Indianapolis, IN; 3Philadelphia Hand to Shoulder Center, Philadelphia, PA; 4Dept of Orthopaedics, Division of Plastic Surgery, Wright State University, Boonshoft School of Medicine / Miami Valley Hospital, Dayton, OH; 5NYC Health + Hospitals/Elmhurst, Queens, NY; 6Division of Plastic and Reconstructive Surgery, The Ohio State University Wexner Medical Center, Columbus, OH; 7University of Colorado, Aurora, CO; 8Youssra Marjoua, MD - Surgery of the Hand and Upper Extremity, Lutherville-Timonium, MD; 9Axogen, Alachua, FL
IntroductionAccurate assessment of the zone of injury of a transected nerve continues to be a challenge for peripheral nerve surgeons. The transected nerve is typically evaluated using loupe magnification, or the operative microscope, prior to trimming the nerve back. In order to reduce the gap, or obviate the need for a nerve graft, surgeons may under-resect the nerve, which may lead to poor regenerative outcomes and neuroma formation. In some instances, the zone of injury simply may not be readily apparent, leading to under-resection. This study characterized the zone of injury of cadaveric peripheral nerves after simulated traumatic lacerations using a kitchen knife, broken glass, or table saw. We utilized a novel high-resolution micro-computed-tomography (micro-CT) imaging of lacerated nerves to characterize the extent of tissue damage.
Materials and MethodsTwelve human upper extremity specimens were lacerated. Each type of injury was created in four specimens at flexor tendon anatomical zone II or V. Lacerations were evaluated by seven surgeons experienced in peripheral nerve repair, and the zone of injury was estimated. Twelve distal and proximal nerve sample pairs were collected and analyzed using micro-CT. The nerve samples were then imaged using the SkyScan 1272 CMOS Edition scanner with maximum spatial resolution of 5 microns. Images were processed using CTVox software.
ResultsThe zone of injury was greater for proximal nerve injuries than distal nerve injuries, as estimated by seven experienced peripheral nerve surgeons for nerve lacerations in Zones II and V (Figure 1). Micro-CT image analysis revealed fascicular damage of the nerves extending proximally and distally from the area of transection (Figure 2), which was routinely underestimated by visual assessment.
ConclusionsThis study highlighted two important trends in zone of injury identification. First, proximal injuries tended to have a larger zone of injury than distal injuries. Second, micro-CT analysis showed that the zone of injury was typically underestimated by visual inspection. While this adjunctive technique is not currently entirely feasible in the operating room, it allows us to study whether or not surgeons tend to under-resect complex nerve injuries when compared to micro-CT evaluation.
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